Heretofore, ferite resonance isolators utilizing hexagonal ferrite materials have never been designed or built having the capability of operating in the millimeter wave frequency range in dielectric waveguide transmission line. Field displacement isolators of ferrite type have been designed and built in dielectric waveguide in the millimeter region, but these devices require large, heavy and impractical permanent biasing magnets and operate over limited bandwidths (&lt;10%).